1. Field of the Invention
This invention relates to a system with which to substantially complete the reaction of chemical with the sulfur dioxide in a mixture of gases. More particularly, the invention relates to constructively increasing the residence time provided by the reaction tank of an Air Quality Control System (AQCS) to fully utilize the unreacted chemical bled from the system.
2. Description of the Prior Art
The AQCS has been developed to remove SO.sub.2 from combustion gases by contacting the gas mixture with a slurry of water and lime/limestone. The cost of the additive lime/limestone has increased with the depreciation of fiat currency value. One way to counter the economic results of this deterioration is to discover and develop systems which are more efficient in utilizing the chemical to combine with SO.sub.2.
Lime combines with SO.sub.2 more efficiently than limestone. But with both additives, as chemicals, their dissolution rates are an important factor in their reactions with SO.sub.2. It is the dissolution rates and the conditions existing in the reaction tank of the AQCS which must be improved.
Obviously, a simple increase in size of the reaction tank will gain residence time within which the desired chemical reaction will take place. However, a practical limit to the size of this tank is quickly reached in design. Additionally, the power requirement for mixing the chemicals and SO.sub.2 in the tank quickly becomes excessive.
Examination of the AQCS cycle attracts attention to the feed stream of the gas mixture to the conventional scrubber tank. If the SO.sub.2 upstream of the AQCS scrubber tank can be used to form a highly acidic liquid stream, that stream can be shifted to the exit of the system to react with the chemical not utilized. The chemical conventionally bled from the system can then be provided adequate residence time to fully react with SO.sub.2 coming to the system.